bmw329 Posted September 17, 2012 Report Share Posted September 17, 2012 Hi Guys, When data logging on the M50B25TU plug in, my vehicle speed is only logging correctly under acceleration. At a cruising speed it drops to around 7 kph, but fluctuates quite a bit (up to around 30 kph). My speed during this time is constant at 100 kph. The sensor itself is wired to cluster then the cluster outputs a signal to the ECU. The cluster is working normally with no variations in speed. Did I miss something on the speed sensor setup or is this a symptom of a bad sender/cluster? Thanks Quote Link to comment Share on other sites More sharing options...
bmw329 Posted November 7, 2012 Author Report Share Posted November 7, 2012 Hi everyone, still scratching my head over this one. I have attached a picture of the output during a relatively stable rpm. As you can see the DI#1 frequency is extremely inconsistent when the rpm and *real* ground speed is constant. Maybe I misunderstand how these are suppose to work, but I think the frequency should be stable for any particular speed of rotation at the diff (where the sensor is located). I am leaning towards a bad sender, so I might just pull the trigger and buy one. But I really hate being disappointed. Anyone have some insight? Quote Link to comment Share on other sites More sharing options...
nissan200sx.dk Posted November 7, 2012 Report Share Posted November 7, 2012 Could it be wrong polarity? Quote Link to comment Share on other sites More sharing options...
bmw329 Posted November 7, 2012 Author Report Share Posted November 7, 2012 Hmm. Don't think so. Its a Vi-PEC pnp. The signal is grounded before it gets to the ecu and the only lead to the ecu is the stock signal wire. Quote Link to comment Share on other sites More sharing options...
Simon Posted November 7, 2012 Report Share Posted November 7, 2012 Couple of things to check. You can try turning the pullup off and then back on again in the ECU on that DI. I would also suggest checking the wiring to the sensor as i have now seen a number of BMW's where the wiring is in a bad way and the insulation is coming off the wires causing shorts. Quote Link to comment Share on other sites More sharing options...
bmw329 Posted October 16, 2013 Author Report Share Posted October 16, 2013 Thought I'd follow up.. after a almost a year. Today I went and bought another cluster and it sorted out the VSS output (95 325is cluster -> 96 328is cluster). From what I could figure, the old cluster's processor wasn't outputting 5V DC to the sensor circuit consistently. The reed switch opens on a tooth, so it drops the voltage to 0. But since the cluster wasn't putting out a consistent 5V each voltage drop was being read as another "tooth". Anyway, thought I'd post in case someone else has a similar situation. Quote Link to comment Share on other sites More sharing options...
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